244 MANUAL OF FRUIT DISEASES 
better than the fungi concerned in the other diseases mentioned. 
If not controlled, the oidium does considerable damage in 
western vineyards. In the Chautauqua region of New York 
growers may in cases of severe infestation lose fifty per cent of 
their grapes on account of shelling due to the powdery-mildew 
fungus. The Lindley is very susceptible to the disease. 
Symptoms. 
All green parts of the vine may be affected: leaves, canes, 
flowers and fruit. The young leaves at first show whitish or 
greenish white patches on the upper or lower surfaces. A 
mottled appearance is thus produced. These patches later 
run together until a large portion of the leaf is covered with a 
grayish white mildew. Sometimes this dense growth of the 
pathogene is accompanied by malformation and discoloration 
of the affected leaf. A vine with diseased foliage has a wilted 
and dwarfed aspect; this is particularly true in the earlier 
parts of the season and in warm, dry weather. An affected 
vine emits a moldy odor. Eventually black, pimple-like fruit- 
bodies of the fungus are seen scattered over the mildewed area. 
Often the mildew is abundant on the shoots. It appears 
near the base of the canes and at first is not noticeable; later 
the affected portion acquires a grayish tint and it is then more 
easily seen. In severe cases whole canes are covered ; in mild 
attacks the mildew is confined to patches. Later affected canes 
turn dark, owing to the injury to the outer bark-cells. If young 
canes are affected, they fail to mature properly and often they 
become blackened over their whole surface; this appearance is 
sometimes mistaken for anthracnose. 
Sometimes the mildew appears on the flowers, if conditions 
are favorable in the vineyard during blossoming. This occurs 
regularly in France, but does not occur in eastern United States. 
Affected blossoms fail to set or develop in an aborted fashion. 
Diseased young berries are dwarfed and are caused to drop. 
If not affected until older, the fruit continues to develop, but 
